Process for the preparation of compounds containing perfluoroalkanesulfonic acid groups

ABSTRACT

The invention relates to a method for producing perfluoroalkanesulfonic acid esters and for further transforming the same into the salts thereof. The invention also relates to the use of the produced compounds in electrolytes, batteries, capacitors, supercapacitors, and galvanic cells.

The present invention relates to a process for the preparation ofcompounds containing perfluoroalkanesulfonic acid groups, and to the useof these compounds in batteries, capacitors, supercapacitors andelectrochemical cells.

The spread of portable electronic equipment, such as, for example,laptop and palmtop computers, mobile telephones or video cameras, andthus also the demand for lightweight and high-performance batteries, hasincreased dramatically worldwide in recent years.

In view of this suddenly increased demand for batteries and theassociated ecological problems, the development of rechargeablebatteries with a long service life is of constantly increasingimportance.

Lithium ion batteries and double layer capacitors with very highcapacities (so-called super- or ultracapacitors) represent the currentstate of the art. In both systems, hydrolysis-sensitive and thermallyunstable substances in the form of LiPF₆ or N(C₂H₅)₄BF₄ are currentlyused as conductive salt. In contact with moist air or with residualwater from the sdlvents, HF can form rapidly. Besides the toxicproperties, HF has a very adverse effect on the cycle behaviour and thuson the performance of the electrochemical cells.

Alternatives which have been presented are imides, such asbis(trifluoromethylsulfonyl)imide or bis(pentafluoroethylsulfonyl)imide,or methanides, such as tris(trifluoromethylsulfonyl)methanide andderivatives thereof.

However, quaternary ammonium and phosphonium salts havingperfluoroalkanesulfonate anions have also been developed as conductivesalts for electrochemical cells. However, the synthesis of these saltsis relatively complex, since an intermediate, methyltrifluoromethanesulfonate (methyl triflate), is difficult to prepare.

Methyl triflate is a strong methylating reagent. It is used inpreparative chemistry for introduction of methyl groups, for example inthe methylation of heterocyclic compounds (Yu, Teylor, TetrahedronLetter, 1999 (36), 6661-6664) or the methylation of organosulfurcompounds (Tsuge, Hafta, Chem. Letter, 1997 (9), 945-946). Methyltriflate is significantly more reactive than methyl iodide, dimethylsulfate and methyl toluenesulfonate, the methylating reagents usuallyused in the synthesis of quaternary ammonium and phosphonium salts.

There are various synthetic routes to methyl triflate (Gramstad, J.Chem. Soc., 1956, 173-180 or Beard, J. Org. Chem., 1973 (21),3673-3677). None of the synthetic routes described is suitable forscale-up since they either use very toxic starting materials, such as,for example, dimethyl sulfate, the yields are very low, the reactionproduct has to be purified, or hazardous by-products or waste productsare formed, such as, for example, sulfuric acid contaminated withdimethyl sulfate.

The object of the invention was therefore to provide a simple processfor the synthesis of alkyl perfluoroalkanesulfonates and conductivesalts which can be prepared therefrom.

The object is achieved by a process for the preparation of compoundscontaining perfluoroalkanesulfonic acid groups using a process step inwhich perfluoroalkanesulfonic anhydride is reacted with dialkylcarbonate in the presence of perfluoroalkanesulfonic acid to give analkyl perfluoroalkanesulfonate, the reaction being carried out under ananhydrous atmosphere, for example:

Surprisingly, it has been found that the reaction ofperfluoroalkanesulfonic anhydride takes place virtually-quantitativelyto give the alkylperfluoroalkanesulfonate. Only catalytic amounts ofperfluoroalkanesulfonic acid are necessary; usually only 0.01-0.1 mol ofperfluoroalkanesulfonic acid is necessary per mole ofperfluoroalkanesulfonic anhydride.

The process according to the invention gives alkylperfluoroalkanesulfonates which can be used as alkylating reagents. Theycan be used for the alkylation of heterocyclic compounds ororganophosphorus and organosulfur compounds or for the preparation ofN-methylamino acid with low racemate formation.

In addition, the compounds containing perfluoroalkanesulfonic acidgroups obtained in accordance with the invention can also be employed inelectrochemical cells, primary batteries, secondary batteries,capacitors and/or supercapacitors, for example as solvents.

Furthermore, the esters obtained can be reacted further to giveperfluoroalkanesulfonic acid salts. It is advantageously not absolutelynecessary for the ester initially obtained in accordance with theinvention to be isolated, since unreacted dialkyl carbonates may bepresent as solvents in the subsequent reaction withXR¹, R²R³,

where

-   -   X is P or N, and    -   R¹, R²    -   and R³ are identical or different, are optionally bonded        directly to one another via a single or double bond and are        each, individually or together,        -   hydrogen,        -   an alkyl group having from 1 to 16 carbon atoms, which may            be partially substituted by further groups, preferably F,            Cl, N(C_(n)F_((2n+1−x))H_(x))₂, O(C_(n)F_((2n+1−x))H_(x)),            SO₂(C_(n)F_((2n+1−x))H_(x)), C_(n)F_((2n+1−x))H_(x), where            1≦n≦6 and 0≦x≦2n+1, an optionally substituted aryl group or            an optionally substituted heterocyclic group,        -   an alkylaryl group whose alkylene group has from 1 to 16            carbon atoms and which may be partially substituted by            further groups, preferably F, Cl, Br, NO₂, CN, alkyl, aryl            or a heterocyclic group,        -   an aryl group, which may be partially substituted by further            groups, preferably F, Cl, Br, NO₂, CN, alkyl, aryl or a            heterocyclic group, or        -   a heterocyclic group, which may be partially substituted by            further groups, preferably F, Cl, Br, NO₂, CN, alkyl, aryl            or a heterocyclic group,    -    where one, two or three CH₂ groups of an alkyl or alkylene        group may be replaced by identical or different heteroatoms,        preferably O, NH or N(alkyl) having from 1 to 6 carbon atoms,        and    -    where R¹, R² and R³ cannot simultaneously be perfluorinated or        perchlorinated,        to give the corresponding perfluoroalkanesulfonic acid salts.        After the reaction, the perfluoroalkanesulfonic acid salt        precipitates out. The unreacted ester merely has to be distilled        off, while the remaining perfluoroalkanesulfonic acid is        neutralised using XR¹R²R³ or can be used for further reactions.

In a preferred variant of the process according to the invention, thesubsequent reaction with the ester is carried out using a compoundXR¹R²R³ which is selected from the group consisting ofX(C₂H₅)₃, X(C₃H₇)₃, X(C₄H₉)₃,

where

-   -   X and Y are P or N, and    -   R¹, R²    -   and R³ are, if desired, identical or different and are each,        individually or together,        -   hydrogen,        -   an alkyl group having from 1 to 16 carbon atoms,        -   an alkylaryl group whose alkylene group has from 1 to 16            carbon atoms,        -   an aryl group or        -   a heterocyclic group,    -    where one, two or three CH₂ groups in the ring and/or the alkyl        groups may be replaced by identical or different heteroatoms,        preferably O, NH or N(alkyl) having from 1 to 6 carbon atoms,        and where the ring and/or the alkyl group may be partially        substituted by further groups, preferably by F, Cl,        N(C_(n)F_((2n+1−x))H_(x)x)₂, O(C_(n)F_((2n+1−x))H_(x)),        SO₂(C_(n)F_((2n+1−x))H_(x)), C_(n)F_((2n+1−x))H_(x), where 1≦n≦6        and 0≦x≦2n+1, alkylaryl, aryl and/or a heterocyclic group, and    -    where the alkylaryl group, the aryl group and/or the        heterocyclic group may be partially substituted by further        groups, preferably F, Cl, Br, NO₂, CN, alkyl, aryl or a        heterocyclic group.

This invention likewise relates to perfluoroalkanesulfonic acid salts oftheM^(n+)[OSO₂CF₃]_(n) ⁻type, in which M^(n+) (n=1 or 2) is selected from the following group:

where

-   -   X and Y are P or N, and    -   R¹, R²    -   and R³ are, if desired, identical or different and are each,        individually or together,        -   hydrogen,        -   an alkyl group having from 1 to 16 carbon atoms,        -   an alkylaryl group whose alkylene group has from 1 to 16            carbon atoms,        -   an aryl group or        -   a heterocyclic group,    -    where one, two or three CH₂ groups in the ring and/or the alkyl        groups may be replaced by identical or different heteroatoms,        preferably O, NH or N(alkyl) having from 1 to 6 carbon atoms,        and where the ring and/or the alkyl group may be partially        substituted by further groups, preferably by F, Cl,        N(C_(n)F_((2n+1−x))H_(x))₂, O(C_(n)F_((2n+1−x))H_(x)),        SO₂(C_(n)F_((2n+1−x))H_(x)), C_(n)F_((2n+1−x))H_(x), where 1≦n≦6        and 0≦x≦2n+1, alkylaryl, aryl and/or a heterocyclic group, and    -    where the alkylaryl group, the aryl group and/or the        heterocyclic group may be partially substituted by further        groups, preferably F, Cl, Br, NO₂, CN, alkyl, aryl or a        heterocyclic group.

These perfluoroalkanesulfonic acid salts can be prepared, for example,by the process according to the invention and are used in a variety ofways. Besides their use as conductive salts, for example inelectrolytes, they can also be employed as solvents, in particular asionic liquids. In addition, it is also possible to use the saltsaccording to the invention in chemical catalysis, in particular asphase-transfer catalyst. Phase-transfer catalysis is a synthetic methodwhich is used for a multiplicity of organic reactions and whichfrequently results in high yields under comparatively mild reactionconditions. In most phase-transfer-catalysed reactions, an anion istransported from an aqueous or solid phase or an interface by means ofthe phase-transfer catalyst into an organic phase in which it is reactedwith increased reactivity. The perfluoroalkanesulfonic acid saltsaccording to the invention are therefore suitable, inter alia, for useas ionic liquids or in phase-transfer catalysis. Their use in thisrespect causes no difficulties at all to the person skilled in the art.

In a further particularly preferred variant of the process according tothe invention, perfluoroalkanesulfonic acid salts can be prepared byreacting an ester obtained in accordance with the invention with acompound selected from the following group:

where

-   -   R¹ to R⁵ are identical or different, are optionally-bonded        directly to one another via a single or double bond and are        each, individually or together,        -   hydrogen,        -   a halogen, preferably fluorine, with the proviso that no            N-halogen bond is present,        -   an alkyl group having from 1 to 8 carbon atoms, which may be            partially substituted by further groups, preferably F, Cl,            N(C_(n)F_((2n+1−x))H_(x))₂, O(C_(n)F_((2n+1−x))H_(x)),            SO₂(C_(n)F_((2n+1−x))H_(x)), C_(n)F_((2n+1−x))H_(x), where            1≦n≦6 and 0≦x≦2n+1,        -   an aryl group,        -   an alkylaryl group,        -   a heterocyclic group,        -   an alkylheterocyclic group.

All compounds containing perfluoroalkanesulfonic acid groups prepared inaccordance with the invention, i.e. perfluoroalkanesulfonic acid estersand in particular their salts, can be employed in electrolytes,electrochemical cells, primary and secondary batteries, capacitors,supercapacitors or ultracapacitors, for example as solvents orconductive salts. The salts can be employed as conductive salts hereeither in pure form or in the form of their mixtures. It is alsopossible to use the salts as conductive salt together with further saltsknown to the person skilled in the art.

The compounds containing perfluoroalkanesulfonic acid groups prepared inaccordance with the invention, in particular the salts, can be used inliquid, gel-like, polymeric or solid electrolytes. To this end, mixturescomprising the conductive salts and suitable polymers and/or suitablesolvents can be employed. For the purposes of the present invention, amixture includes pure mixtures of the components, mixtures in which thesalt(s) is (are) included in a polymer or gel, and mixtures in whichchemical and/or physical bonds exist between the salt(s) and a polymeror gel. In the case of a gel-like electrolyte, the mixture preferablycomprises a suitable solvent in addition to the salt(s) and the polymer.

The solvents employed for liquid or gel-like electrolytes areparticularly preferably aprotic solvents or mixtures thereof which aresuitable for use in a primary or secondary battery, a capacitor, asupercapacitor or an electrochemical cell, for example carbonates,esters, ethers, sulfolanes or nitrites, such as, for example, dimethylcarbonate, diethyl carbonate, butylene carbonate, propylene carbonate,ethylene carbonate, ethyl methyl carbonate, methyl propyl carbonate,1,2-dimethoxyethane, 1,2-diethoxyethane, methyl acetate,γ-butyrolactone, ethyl acetate, methyl propionate, ethyl propionate,methyl butyrate, ethyl butyrate, dimethyl sulfoxide, dioxolane,sulfolane, acetonitrile, acrylonitrile, tetrahydrofuran,2-methyltetrahydrofuran or mixtures thereof.

The polymers employed for polymeric or gel-like electrolytes arepreferably homopolymers or copolymers of acrylonitrile, vinylidenedifluoride, methyl (meth)acrylate, tetrahydrofuran, ethylene oxide,siloxane, phosphazene or a mixture of at least two of theabove-mentioned homopolymers and/or copolymers, where it is beingpossible for the polymers to be at least partially crosslinked.

The electrolytes obtained in this way are suitable for use in primarybatteries, secondary batteries, capacitors, supercapacitors orultra-capacitors and electrochemical cells and are likewise asubject-matter of the present invention.

The invention also relates to primary batteries, secondary batteries,capacitors, supercapacitors and electrochemical cells which contain atleast one perfluoroalkanesulfonic acid salt prepared in accordance withthe invention and optionally further salts and/or additives. Thesefurther salts and additives are known to the person skilled in the art,for example from Doron Aurbach, Nonaqtieous Electrochemistry, MarcDekker Inc., New York 1999; D. Linden, Handbook of Batteries, SecondEdition, McGraw-Hill Inc., New York 1995 and G. Mamantov and A. I.Popov, Chemistry of Nonaqueous Solutions, Current Progress, VCHVerlagsgemeinschaft, Weinheim 1994.

The complete disclosure content of all applications, patents andpublications mentioned above and below, and the correspondingapplications DE 101 26 929.3 and DE 101 36 121.1, submitted on01.06.2001 and on 26.07.2001 respectively, are incorporated into thisapplication by way of reference.

The examples of the subject-matter according to the invention which aredescribed below serve merely for explanation and do not restrict thepresent invention in any way. In addition, the invention described canbe carried out in the entire range claimed.

All NMR spectra were measured on a Bruker WP 80 SY spectrometer.

EXAMPLES Example 1 Preparation of methyl trifluoromethanesulfonate(methyl triflate)

646 g (2.29 mol) of trifluoromethanesulfonic anhydride and 36 g (0.24mol) of trifluoromethanesulfonic acid are initially introduced into a 11round-necked flask. 206 g (2.29 mol) of dimethyl carbonate are added atroom temperature with constant stirring and reflux cooling. The solutionwarms to 50-60° C. within 10 minutes and is subsequently stirred at thistemperature for a further 1 hour. The solution is subsequently warmed to100-110° C. using an oil bath and stirred for a further 2 hours. Afterdistillation, 733 g of methyl trifluoromethanesulfonate having a purityof greater than 99% are isolated (boiling range: 98-99° C., yield:97.7%).

¹⁹F- and ¹H-NMR are identical with the literature data (Paquette,Encyclopedia of Reagents for Organic Synthesis, 1995, 3617-3622).

731 g (2.59 mol) of trifluoromethanesulfonic anhydride and 232 g (2.58mol) of dimethyl carbonate are added to the residue, and the processdescribed above is repeated. 837 g of methyl trifluoromethanesulfonatehaving a purity of greater than 99% are isolated (yield: 99.1%).

The process can be repeated a number of times.

Example 2 Preparation of methyl pentafluoroethanesulfonate

5.74 g (15.0 mmol) of pentafluoroethanesulfonic anhydride and 0.31 g(1.55 mmol) of pentafluoroethanesulfonic acid are initially introducedin a 10 ml round-necked flask. 1.35 g (15.0 mmol) of dimethyl carbonateare added at room temperature with constant stirring and reflux cooling.The solution is stirred for one hour at a temperature of 60° C. andsubsequently for a further 3 hours at 110° C. After distillation, 5.41 gof methyl pentafluoroethanesulfonate are isolated (boiling range:114-115° C., yield: 84.1%).

¹⁹F-NMR, ppm: (solvent: CDCl₃; standard: CCl₃F): −80.44 s (CF₃); −115.34s (CF₂)

¹H-NMR, ppm: (solvent: CDCl₃; standard: TMS): 4.23 s (CH₃)

Example 3 Preparation of N-methyl-N-triethylammoniumtrifluoromethanesulfonate

A solution of 8.35 g (82.7 mmol) of triethylamine in 150 cm³ of dryhexane is initially introduced at room temperature. 13.56 g (82.7 mmol)of methyl triflate, prepared as in Example 1, are added at roomtemperature over the course of 10 minutes with constant stirring. Thesolution warms and is stirred for a further half an hour. During this,the solution is returned to room temperature. A white precipitate isfiltered off and washed with hexane. The hexane filtrate can be used fora further reaction. After drying under reduced pressure at 60° C., 21.81g of a white microcrystalline material are isolated (yield: 99.5%).

¹⁹F-NMR, ppm: (solvent: acetonitrile-D₃; standard: CCl₃F): −78.04 s(CF₃SO₃ ⁻)

¹H-NMR, ppm: (solvent: acetonitrile-D₃; standard: TMS): 1.25 tm (3CH₃);2.86 s (CH₃); 3.26 q (3CH₂); J³ _(H,H)=7.3 Hz

¹H-NMR data correspond to the literature data (R. Weiβ, K.-G. Wagner, M.Hertel, Chem. Ber. 117 (1984) pp. 1965-1972)

Example 4 Preparation of methyl(triethyl)phosphoniumtrifluoromethanesulfonate

A solution of 8.05 g (68.2 mmol) of triethylphosphine in 150 cm³ of dryhexane is initially introduced at room temperature. 11.19 g (68.2 mmol)of methyl triflate, prepared as in Example 1, are added at roomtemperature over the course of 10 minutes with constant stirring. Thesolution warms and is stirred for a further half an hour. During this,the solution is returned to room temperature. A white precipitate isfiltered off and washed with hexane. The hexane filtrate can be used fora further reaction. After drying under reduced pressure at 60° C., 19.02g of a white microcrystalline material are isolated (melting point.103-104° C., yield: 98.9%).

¹⁹F-NMR, ppm (solvent: acetone-D₆; standard: CCl₃F): −77.82 s (CF₃SO₃ ⁻)

¹H-NMR, ppm (solvent: acetone-D₆; standard: TMS): 1.30 dt (3CH₃); 1.95 d(CH₃); 2.40 dq (3CH₂); J³ _(H,H)=7.7 Hz; J² _(P,H)=13.7 Hz; J²_(P,H)=13.8 Hz; J³ _(P,H)=18.8 Hz

Elemental Analysis:

found: 33.72% C, 6.57% H, 11.14% S

calculated: 34.04% C, 6.43% H, 11.36% S ((C₂H₅)₃PCH₃ ⁺CF₃SO₃ ⁻)

Example 5 Preparation of 1,3-dimethylimidazoliumtrifluoromethanesulfonate

13.70 g (83.5 mmol) of methyl triflate are added dropwise over thecourse of 10 minutes to 6.67 g (81.2 mmol) of 1-methylimidazole in around-bottomed flask with stirring and ice-bath cooling. The reactionmixture warms and is stirred at 70-75° C. for one hour with refluxcooling. The excess methyl triflate is removed at 60° C. under reducedpressure. 20.00 g of a white powder are isolated.

¹⁹F-NMR, ppm (solvent: acetonitrile-D₃; standard: CCl₃F): −78.14 s(CF₃SO₃)

¹H-NMR, ppm (solvent: acetonitrile-D₃; standard: TMS): 3.82 s (2CH₃);7.35 d (2H); 8.53 t (1H); J⁴ _(H,H)=1.6 Hz

¹H-NMR data correspond to the literature data (U. Zollner, Tetrahedron,44, No. 24 (1988), pp. 7413-7426)

Example 6 Preparation of N,N-dimethylpyrrolidiniumtrifluoromethanesulfonate

A solution of 6.83 g (80.2 mmol) of N-methylpyrrolidine in 150 cm³ ofdry hexane is initially introduced at room temperature. 13.12 g (80.2mmol) of methyl triflate, prepared as in Example 1, are added at roomtemperature over the course of 10 minutes with constant stirring, duringwhich the solution warms. After half an hour, the solution is returnedto room temperature. The white precipitate deposited is filtered off,washed with hexane and dried at 60° C. under reduced pressure. 16.61 gof a white microcrystalline material are isolated (melting point (withdecomposition): 308-310° C., yield 98.3%).

¹⁹F-NMR, ppm (solvent: acetonitrile-D₃; standard: CCl₃F −78.00 s (CF₃SO₃⁻)

¹H-NMR, ppm (solvent: acetonitrile-D₃; standard: TMS): 2.17 m (2H); 3.07s (CH₃); 3.45 m (2H)

Elemental Analysis after Recrystallisation from Methanol:

found: 33.66% C, 5.68% H, 5.60% N, 13.06% S

calculated: 33.73% C, 5.66% H, 5.62% N, 12.86% S(C₇H₁₄F₃NO₃S)

Example 7 Preparation of N,N-dimethylpiperidiniumtrifluoromethanesulfonate

A solution of 7.76 g (78.2 mmol) of N-methylpiperidine in 150 cm³ of dryhexane is initially introduced at room temperature. 12.83 g (78.2 mmol)of methyl triflate, prepared as in Example 1, are added at roomtemperature over the course of 10 minutes with constant stirring, duringwhich the solution warms. After half an hour, the solution is returnedto room temperature. The white precipitate deposited is filtered off,washed with hexane and dried at 80° C. under reduced pressure. 19.72 gof a white microcrystalline material are isolated (melting point afterrecrystallisation from methanol: 255-256° C., yield 95.8%).

¹⁹F-NMR, ppm (solvent: acetonitrile-D₃; standard: CCl₃F): −78.06 s(CF₃SO₃ ⁻)

¹H-NMR, ppm (solvent: acetonitrile-D₃; standard: TMS): 1.79 m (3CH₂);3.02 s (2CH₃); 3.27 m (2CH₂)

Elemental Analysis after Recrystallisation from Methanol:

found: 36.44% C, 6.07% H, 5.31% N, 12.20% S

calculated: 36.50% C, 6.13% H, 5.32% N, 12.18% S(C₈H₁₆F₃NO₃S)

1-5. (canceled)
 6. A compound of the formulaM^(n+)[OSO₂CF₃]_(n) ⁻, in which M^(n+) (n=1 or 2) is

X and Y are P or N, and R¹, R² and R³ are identical or different and areeach, individually or together, hydrogen, an alkyl group having from 1to 16 carbon atoms, an alkylaryl group whose alkylene group has from 1to 16 carbon atoms, an aryl group or a heterocyclic group,  where one,two or three CH₂ groups in the ring and/or the alkyl groups may bereplaced by identical or different heteroatoms, preferably O, NH orN(alkyl) having from 1 to 6 carbon atoms, and  where the ring and/or thealkyl group may be partially substituted by further groups, preferablyby F, Cl, N(C_(n)F_((2n+1−x))H_(x))₂, O(C_(n)F_((2n+1−x))H_(x)),SO₂(C_(n)F_((2n+1−x))H_(x)), C_(n)F_((2n+1−x))H_(x), where 1≦n≦6 and0≦x≦2n+1, alkylaryl, aryl and/or a heterocyclic group, and  where thealkylaryl group, the aryl group and/or the heterocyclic group may bepartially substituted by further groups, preferably F, Cl, Br, NO₂, CN,alkyl, aryl or a heterocyclic group.
 7. An electrolyte, comprising acompound according to claim 6, optionally mixed with other salts. 8.Primary batteries, secondary batteries, capacitors, supercapacitors orelectrochemical cells, comprising a conductive salt which is a compoundof claim 6, optionally in combination with further salts.
 9. A liquid,gel, polymeric or solid electrolyte comprising one or more compoundsaccording to claim 6, optionally mixed with other salts.
 10. Primarybatteries, secondary batteries, capacitors, supercapacitors and/orelectrochemical cells comprising one or more compounds according toclaim
 6. 11. A solvent comprising one or more compounds according toclaim
 6. 12. A phase-transfer catalyst comprising one or more compoundsaccording to claim
 6. 13-15. (canceled)
 16. Primary batteries, secondarybatteries, capacitors, supercapacitors and/or electrochemical cellscomprising electrolytes according to claim 9.